Author:

M. Umair Siddiqui(West Virginia University)

We present a history of research on the magnetized plasma boundary and
recent first measurements of particle flows in such structures in laboratory
plasmas using multi-dimensional laser-induced fluorescence (LIF). Our
measurements show that the canonical model for this boundary proposed in
1982 [\textit{Chodura, Phys. Fluids (1982)}] is inaccurate for systems where the ion-neutral collision length is less than at least 4 times the ion gyro radius. Rather, our measurements validate more sophisticated plasma boundary fluid models that take neutral
collisions into account [\textit{Riemann, Phys. Plasmas (1994); Ahedo, Phys. Plasmas (1997); Siddiqui et al., Phys. Plasmas (2014)}]. In light of these results, we show that both three-dimensional ion and neutral velocity distribution functions are
strongly affected near the boundary. We discuss effects of these perturbed
distributions on wall loading and erosion in experiments and applications
such as divertor tokamak scrape-off layers and Hall thrusters. Finally, we
propose modern definitions of the oft-used term, ``magnetic presheath.''

*This work is supported by U.S. National Science Foundation grant number PHY-1360278.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2015.DPP.TI2.3